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Date: Wed, 20 Jan 2016 17:47:27 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Byungchul Park <byungchul.park@lge.com>,
        Chris Metcalf <cmetcalf@ezchip.com>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Mike Galbraith <efault@gmx.de>, Rik van Riel <riel@redhat.com>
Subject: Re: [RFC PATCH 4/4] sched: Upload nohz full CPU load on task
 enqueue/dequeue
Message-ID: <20160120164726.GD24537@lerouge>
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On Wed, Jan 20, 2016 at 10:42:56AM -0600, Christoph Lameter wrote:
> On Wed, 20 Jan 2016, Frederic Weisbecker wrote:
> 
> > > So we agreed long time ago, that we first fix the issues with s single task
> > > running undisturbed in user space, i.e. tickless. Those issues have never been
> > > resolved fully, but now you try to add more complexity of extra runnable
> > > tasks, nohz tasks sleeping and whatever.
> >
> > Nohz tasks do sleep, really, at least we need to handle that case now.
> 
> Sleep meaning call into the OS to be put to sleep?

Indeed, when the task has finished its work, it goes to sleep, right?

> Why would NOHZ be active then?

It's active when the task active.